Plasma process device

ABSTRACT

A plasma processing apparatus includes: a processing chamber; an inlet waveguide having an interior space in which a first standing wave of a microwave is formed by means of resonance; a dielectric within which a second standing wave of the microwave is formed by means of resonance; and a slot antenna having a slot through which the microwave is passed from the interior space to the dielectric. The slot is generally located at a point where the position of a loop in the first standing wave orthogonally projected to the slot antenna coincides with the position of a loop in the second standing wave orthogonally projected to the slot antenna. The present invention provides a plasma processing apparatus that improves the propagation efficiency of a microwave passed through an aperture of the slot antenna, thereby allowing microwave energy to be efficiently introduced into a processing chamber.

TECHNICAL FIELD

The present invention is related generally to a plasma processingapparatus, and more particularly, to a plasma processing apparatus suchas dry etching equipment, deposition equipment and ashing systems usedin manufacturing processes of semiconductors, liquid crystal displaydevices and solar cells, for example.

In recent years, plasma processing equipment has been developed toprocess a substrate with a greater surface area to cope withincreasingly greater substrate surfaces used in the manufacturing ofsemiconductors or flat panel displays (FPDs) such as liquid crystaldisplays (LCDs). Particularly, FPD manufacturing equipment is beingdeveloped targeted for substrates with a side of one meter or greater.When a plasma processing apparatus performs microtreatments anddeposition on such large substrates, how to create a uniform plasma andto ensure consistent processes such as various treatments and depositionis a major concern.

In terms of uniformity of a plasma and consistency in processing as wellas their control, plasma processing equipment using inductive couplingor a power supply at frequencies in the microwave range (frequenciesranging from 100 MHz to 10 GHz) achieves better results than that usingcapacitive coupling which was mainly employed, since the former type isconfigured such that the power for the plasma source can be controlledindependently from the power for biasing the substrate. This facilitatesprocess control, resulting in increasingly wide use of this type.

A plasma processing apparatus using a power source at frequencies in themicrowave range is typically configured to introduce microwave energydirected by a waveguide or a coaxial cable into the processing chamberthrough a dielectric that serves as a slot antenna as well as a vacuumseal.

In a plasma processing apparatus for larger substrates, a plurality ofslots are typically provided in the slot antenna. The position of thecenter of each of the slots and the distance between them are criticalin whether microwave energy from the source can be efficientlyintroduced into the processing chamber.

Prior documents disclosing the positioning of slots include JapanesePatent Laying-Open Nos. 11-121196 and 10-241892. FIG. 8 is a crosssectional view of a microwave plasma processing apparatus disclosed inJapanese Patent Laying-Open No. 11-121196.

Referring to FIG. 8, on top of a reactor 101 that defines a processingchamber 102 therewithin, a sealing plate 104 is provided, which isformed by a dielectric. The upper surface of sealing plate 104 iscovered with a cover member 110. A waveguide type antenna 112 isprovided on top of cover member 110 to introduce a microwave intoprocessing chamber 102. Waveguide type antenna 112 is connected via awaveguide 121 to a microwave oscillator 120 that provides an oscillatingmicrowave. One end of waveguide type antenna 112 which is linear-shapedis connected with waveguide 121. The other, arced, end of waveguide typeantenna 112 forms a closed end above reactor 101. A plurality of slits115 are provided in the portion of cover member 110 that are belowwaveguide type antenna 112.

An oscillating microwave generated by microwave oscillator 120 issuperimposed within waveguide type antenna 112 on a wave reflected fromthe end of antenna 112. This results in a standing wave within antenna112. Each slit 115 is provided at n·λg/2 (n is a natural number and λgis the wavelength of the microwave) from the end of waveguide typeantenna 112.

FIG. 9 is a cross sectional view of a plasma processing apparatusdisclosed in Japanese Patent Laying-Open No. 10-241892. Referring toFIG. 9, a plasma processing apparatus 220 includes a processing chamber222 defined by a chamber body 221, and a plasma generating space 226above processing chamber 222. An oscillator 229 is provided spaced apartfrom chamber body 221 for generating a microwave. A waveguide 230 isprovided above plasma generating space 226. One end of waveguide 230 isconnected with oscillator 229 and the other end of waveguide 230 has ashort-circuit surface 230 a that reflects a microwave. A top plate 231having a slot antenna formed therein, not shown, is provided close tothe other end of waveguide 230. A microwave transmissive window 233,formed by a dielectric, is provided below top plate 231. Microwavetransmissive window 233 is attached to an attachment 234 on the wallthat defines plasma generating space 226.

Microwave transmissive window 233 forms a composite wave from anincident microwave advancing toward an attachment 234 and a reflectedmicrowave reflected from this attachment 234. The width W of microwavetransmissive window 233 is determined to satisfy W=λsw/2×n (λsw is thewavelength of the microwave, and n is an integer). A slot antenna isprovided at λsw/2 away from the end of microwave transmissive window233.

A microwave plasma processing apparatus disclosed in Japanese PatentLaying-Open No. 11-121196 directs a microwave from microwave oscillator120 in the direction of processing chamber 102 through waveguide typeantenna 112. The microwave that has reached sealing plate 104 throughslit 115 is then directed toward processing chamber 102. Unfortunately,slits 115 are only positioned based on the wavelength of the microwavepropagating through waveguide type antenna 112, and sealing plate 104 isthus not taken into consideration, such that some configurations ofsealing plate 104 and some relative dielectric constants of thedielectric forming sealing plate 104 may prevent a microwave from beingefficiently introduced into processing chamber 102.

A plasma processing apparatus 220 disclosed in Japanese PatentLaying-Open No. 10-241892 directs a microwave from oscillator 229 in thedirection of plasma generating space 226 through waveguide 230. Themicrowave that has reached microwave transmissive window 233 through theslot antenna is then introduced into plasma generating space 226.Unfortunately, the slot antenna is positioned without taking e.g. theconfiguration of waveguide 230 into consideration, such that someconfigurations of waveguide 230 may prevent a microwave from beingefficiently introduced into plasma generating space 226. Moreover,positioning the slot antenna away from the end of microwave transmissivewindow 233 at a distance of λsw/2 is inappropriate for efficientlyintroducing a microwave.

An object of the present invention is to solve the above problems byproviding a plasma processing apparatus that provides improvedpropagation efficiency of a microwave passed through an aperture in aslot antenna to allow microwave energy to be efficiently introduced intoa processing chamber.

DISCLOSURE OF THE INVENTION

A plasma processing apparatus according to the present inventionincludes: a processing chamber for performing plasma-assistedprocessing; microwave introducing means having an interior space inwhich a first standing wave of a microwave is formed by means ofresonance, the microwave introducing means directing the microwave tothe processing chamber; a dielectric provided between the processingchamber and the microwave introducing means and adjacent the interiorspace for directing the microwave into the processing chamber, a secondstanding wave of the microwave being formed within the dielectric bymeans of resonance; and a slot antenna covering a side of the dielectricthat faces the interior space. The slot antenna has an aperture-throughwhich the microwave is passed from the interior space to the dielectric.The aperture is generally located at a point where the position of aloop in the first standing wave orthogonally projected to the slotantenna coincides with the position of a loop in the second standingwave orthogonally projected to the slot antenna.

A plasma processing apparatus constructed as described above has anaperture in the slot antenna at a position corresponding to loops in thefirst and second standing waves. A loop in a standing wave means theportion of a microwave at which its electric field strength is at itsmaximum, and a node in a standing wave means the portion of a microwaveat which its electric field strength is at its minimum. Loops and nodesin a standing wave appear alternately at a certain distance (¼ of thewavelength of the microwave). Accordingly, a microwave can be propagatedfrom the interior space to the dielectric through the aperture with itsdirection kept constant. As a result, the propagation efficiency of amicrowave can be improved and microwave energy can be efficientlyintroduced into the processing chamber.

Preferably, a plurality of apertures are provided at a distance d. Whenthe wavelength of the microwave in the interior space in which the firststanding wave is formed is represented by λp and the wavelength of themicrowave within the dielectric in which the second standing wave isformed is represented by λq, the distance d between the aperturessatisfies d=m·λp/2 (m is a natural number) and d=n·λq/2 (n is a naturalnumber). A plasma processing apparatus constructed as described aboveprovides loops in the first and second standing waves appearing at λp/2and λq/2, respectively. Accordingly, natural numbers m and n thatsatisfy m·λp/2=n·λq/2 are calculated and, from these m and n, thedistance d is determined at which apertures are to be provided.Apertures can then be provided at the distance d such that the aperturesare located at positions corresponding to loops in the standing waves.

Preferably, the first and second standing waves have electric fieldssubstantially in one and the same direction at those loops in the firstand second standing waves which are projected to one and the sameaperture. A plasma processing apparatus constructed as described abovecan reduce the variation in the orientation of an electric field for anyof the plurality of apertures, thereby minimizing reflected wave. Thus,microwave energy can be introduced into the processing chamber stillmore efficiently.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross sectional view of a plasma processing apparatus in afirst embodiment of the present invention.

FIG. 2 is a cross sectional view of the apparatus along the line II-IIin FIG. 1.

FIG. 3 is a cross sectional view of the apparatus illustrating theelectric field strength of standing waves formed in the interior spaceand dielectrics using a simulation in the first embodiment.

FIG. 4 is a schematic view illustrating the positions of standing wavesformed in the interior space and dielectrics relative to slots inanother simulation for comparison.

FIG. 5 is another schematic view illustrating the positions of standingwaves formed in the interior space and dielectrics relative to slots inyet another simulation for comparison.

FIG. 6 is yet another schematic view illustrating the positions ofstanding waves formed in the interior space and dielectrics relative toslots in still another simulation for comparison.

FIG. 7 is a cross sectional view of an apparatus illustrating theelectric field strength of standing waves formed in the interior spaceand dielectrics using a simulation in a second embodiment.

FIG. 8 is a cross sectional view of a microwave plasma processingapparatus disclosed in Japanese Patent Laying-Open No. 11-121196.

FIG. 9 is a cross sectional view of a plasma processing apparatusdisclosed in Japanese Patent Laying-Open No. 10-241892.

BEST MODES FOR CARRYING OUT THE INVENTION

Embodiments of the present invention will now be described withreference to the drawings.

First Embodiment

In the present embodiment, the structure of a plasma processingapparatus will be described below, where the plane along which the papersurface of FIG. 1 extends is defined as the X-Z plane while the planealong which the paper surface of FIG. 2 extends is defined as the Y-Zplane.

Referring to FIGS. 1 and 2, a plasma processing apparatus includes aprocessing chamber body 2 that has an aperture on its top surface anddefines a processing chamber 13 therewithin, a chamber lid 1 provided ontop of processing chamber body 2, a dielectric 5 provided in chamber lid1, a slot antenna 6, and an inlet waveguide 4.

Within processing chamber 13, a substrate holder 7 is attached toprocessing chamber body 2 with an interposed insulator 12. A substrate9, on which plasma processing in processing chamber 13 is performed, isplaced on the top surface of substrate holder 7. A gasket 10 is providedat the contact between chamber lid 1 and processing chamber body 2 toensure the sealing. Processing chamber 13 is connected to a vacuum pump,not shown.

Chamber lid 1 has a plurality of rectangular apertures 1 a spaced apartfrom each other at a certain distance. Four apertures 1 a form a rowalong the X direction, while two form a column along the Y direction.Each aperture 1 a has a dielectric plate 5 fitted therein via a gasket11 for sealing. Dielectric 5 is formed of alumina (Al₂O₃).

Dielectric 5 serves to vacuum seal processing chamber 13 as well as topropagate a microwave therethrough. A vacuum pump, not shown, may beoperated to keep processing chamber 13 evacuated at around 10⁻⁴ Pa to10⁻⁵ Pa. A gas introducing conduit 14 is provided in chamber lid 1 tointroduce a process gas into processing chamber 13.

Although not shown, a temperature regulator is provided at chamber lid1, processing chamber body 2 and substrate holder 7 in order to keep aconstant temperature.

A slot antenna 6 is provided on the top surface of dielectric 5, i.e.opposite the side facing processing chamber 13. Slot antenna 6 extendsto cover the entire top surface of dielectric 5. A slot antenna 6 has aplurality of slots 6 a arranged along the Y direction.

Inlet waveguide 4 is provided on slot antenna 6. Inlet waveguide 4defines an interior space 20 adjacent slot 6 a formed in slot antenna 6.Interior space 20 has a size in the Y direction that is longer than thatin the X direction. Atop inlet waveguide 4 is provided a waveguide 3communicating with interior space 20. Waveguide 3 is connected with amagnetron, not shown, via a microwave circuit, also not shown. Themicrowave circuit is composed of an isolator, an automatic matchingdevice, and a Japanese Industrial Standard (JIS) compatible straightwaveguide, corner waveguide, taper waveguide and branch waveguide andthe like.

The further description below assumes that the plasma processingapparatus shown in FIGS. 1 and 2 are used for dry etching equipment.

A microwave generated from a magnetron, not shown, at a frequency of2.45 GHz, for example, is passed through a microwave circuit, not shown,to reach waveguide 3. The microwave further advances through waveguide 3to interior space 20 and propagates through a slot 6 a in slot antenna 6to dielectric 5. The microwave is then directed through dielectric 5 toprocessing chamber 13.

The microwave directed to processing chamber 13 energizes a process gascomposed of, for example, CF₄, Cl₂, O₂, N₂ or Ar or a gaseous mixturethereof, introduced through gas introducing conduit 14. As a result, theprocess gas becomes a plasma (ionized gas). The plasma is utilized toetch substrate 9 placed on substrate holder 7 (for example, a glasssubstrate on which a single layer or a stack made of a metal such as Alor an insulator is deposited with a resist placed thereon used informing interconnects or contact holes).

Rendering a process gas into a plasma generally requires more energy forgreater surface area of the work piece i.e. a substrate. Accordingly,processing a substrate with a large surface area, such as with a sidegreater than one meter, requires a total supply output of a plasmaprocessing apparatus of several kW to tens of kW. Thus, it is crucial tobe able to introduce microwave energy into processing chamber 13 asefficiently as possible.

In particular, suppose that a microwave at high frequencies, for example2.45 GHz is introduced; then, the wavelength of the microwave in a freespace will be 122 mm. Thus, the wavelength of the microwave is shorterthan the substrate size. Consequently, when a microwave with frequencieson the order of GHz is used, the size of the waveguide, the position ofthe slots and the distance between them, the relative dielectricconstant and the size of the dielectric and the like are critical inappropriately controlling propagation properties of the microwave andthe consistency in processing.

In other words, inlet waveguide 4 and dielectric 5 through which amicrowave is passed before being introduced into processing chamber 13serve as a resonator to form a standing wave of the microwave withininterior space 20 and dielectric 5. For a microwave with a wavelength λ,a node, at which the electric field strength is at its minimum, appearsat every λ/2 in a standing wave, and a loop, at which the electric fieldstrength is at its maximum, appears at every λ/2 separated from a nodeby λ/4. The ends of interior space 20 and the ends of dielectric 5provide fixed ends of an electric field and thus always correspond tonodes in a standing wave.

The configuration of inlet waveguide 4 and dielectric 5, as well as therelative dielectric constant of dielectric 5 are such that the positionof a loop in a standing wave in interior space 20 orthogonally projectedto slot antenna 6 may coincide with the position of a loop in a standingwave in dielectric 5 orthogonally projected to slot antenna 6, where thepositions of the loops in the standing waves in interior space 20 and indielectric 5 can be determined by a computer simulation using theconfigurations of inlet waveguide 4 and dielectric 5 as well as therelative dielectric constant of dielectric 5 as parameters.

A slot 6 a is located at a point where the position of a loop in astanding wave in interior space 20 orthogonally projected to slotantenna 6 coincides with the position of a loop in a standing wave indielectric 5 orthogonally projected to slot antenna 6. In other words,each slot 6 a is formed on slot antenna 6 directly below a loop in astanding wave in interior space 20 and directly above a loop in astanding wave in dielectric 5.

For such positioning of slots 6 a, since a standing wave of a microwavehas a loop at every λ/2, the distance d between slots 6 a can berepresented as: d=m·p/2=n·λq/2 (in and n are arbitrary natural numberssatisfying the above equation, λp is the wavelength of a microwaveformed in interior space 20, and λq is the wavelength of a microwaveformed in dielectric 5).

A plasma processing apparatus according to the first embodiment of thepresent invention includes: a processing chamber 13 for performingplasma-assisted processing; an inlet waveguide 4 as microwaveintroducing means which has an interior space 20 in which a firststanding wave of a microwave is formed by means of resonance, thewaveguide directing the microwave toward processing chamber 13; adielectric 5 provided between processing chamber 13 and inlet waveguide4 and adjacent interior space 20 to direct the microwave into processingchamber 13, a second standing wave of the microwave being formed withinthe dielectric by means of resonance; and a slot antenna 6 having a slot6 a that serves as an aperture through which the microwave is passedfrom interior space 20 into dielectric 5, the antenna covering the sideof dielectric 5 facing interior space 20. Slot 6 a is generally locatedat a point where the position of a loop in the first standing waveorthogonally projected to slot antenna 6 coincides with the position ofa loop in the second standing wave orthogonally projected to slotantenna 6.

A plurality of slots 6 a are provided at the distance d. The distance dsatisfies d=n·λp/2 (n is a natural number) and d=m·λq/2 (m is a naturalnumber), where λp is the wavelength of the microwave in interior space20 in which the first standing wave is formed, and λq is the wavelengthof the microwave in dielectric 5 in which the second standing wave isformed.

A plasma processing apparatus thus configured allows microwave energy tobe efficiently introduced into the processing chamber. In other words,the magnetic field is relatively strong directly below a loop in astanding wave in interior space 20, such that a slot 6 a provided thereallows a large current to be induced around slot 6 a. This current inturn induces a large magnetic field from slot 6 a. Further, a wave suchas a microwave typically has higher propagation efficiency whenpropagated in a straight line. Wave propagation in a curve will resultin a reflected wave at the curved point, resulting in lower propagationefficiency. In the present embodiment, slot 6 a is located directlyabove a loop in a standing wave in dielectric 5, such that a microwavecan be propagated in a straight line through slot 6 a from interiorspace 20 to dielectric 5. In this way, the energy loss of a microwaveduring propagation can be minimized. For the above reasons, thepropagation efficiency of a microwave can be improved whereby microwaveenergy can be efficiently introduced into processing chamber 13.

A simulation was conducted on a computer as described below to enablethe designing of an actual plasma processing apparatus in the presentembodiment.

A microwave generated from a magnetron, not shown, was rendered to thatof a single mode TE (1, 0) by means of a JIS waveguide, and themicrowave was able to be propagated in a single mode TE (1, 0) through astraight waveguide, corner waveguide, taper waveguide and branchwaveguide and the like. The single mode TE (1, 0) was able to beefficiently converted to another mode and the microwave was able to beintroduced into processing chamber 13.

Here, s and t in the TE (s, t) mode each indicates a mode of a wave. Atransverse electric (TE) wave is a wave in which the direction of anelectric field only lies on a plane (e.g. the X-Y plane) perpendicularto the direction in which the electromagnetic wave advances (e.g. the Zdirection). s indicates the mode of one direction (e.g. the X direction)component representing the direction of that electric field, while tindicates the mode of a direction (e.g. the Y direction) componentperpendicular to the direction indicated by s. The TE (1, 0) modeindicates a fundamental wave that can be propagated by a square(rectangular) waveguide, and greater values for s and t mean a mode of awave of higher orders (harmonic).

First, an inlet waveguide 4 was designed such that an interior space 20had dimensions of 16 mm in the X direction, 530 mm in the Y direction,and 100 mm in the Z direction. Thus, inlet waveguide 4 serves as a modeconverter that converts a microwave of the TE (1, 0) mode into amicrowave of the TE (7, 0) mode.

FIG. 3 is an enlarged view of the cross section of interior space 20 andneighboring components shown in FIG. 2, where some details are omitted.

Referring to FIG. 3, an electromagnetic field simulation was conductedto determine the electric field strength distribution of a standing waveof a microwave formed in interior space 20. Near-circles in the figureare contour lines illustrating the electric field strength of a standingwave and indicate stronger field strength toward the center of thenear-circles. The symbols in the middle of the near-circles indicate thedirection of the electric fields, where a circle with a solid filledcenter indicates the direction from the paper plane to the viewer, and acircle with a cross in it indicates the direction from the paper planeto the depth

A standing wave of a microwave with a wavelength λp of about 154 mm inthe y direction was formed in interior space 20. Thus, loops A7 to G7 inthe standing wave were formed at Y coordinates −226 mm, −149 mm, −72 mm,0, 72 mm 149 mm, and 226 mm, where Y coordinate zero represents thecenter of inner space 20 in the Y direction. It should be noted that thedistance between loops C7 and D7 in the standing wave and the distancebetween loops D7 and E7 in the standing wave are smaller than thedistances between the other adjacent loops in the standing wave, sinceinterior space 20 communicates with waveguide 3 above zero on the Ycoordinate axis, which causes a reflected wave at crooked portions ofthe waveguide, causing distortion in the wave.

Table 1 shows exemplary arrangements of slots 6 a with respect to thepositions of loops in the standing wave formed in interior space 20.TABLE 1 Standing wave in End Left Right interior space 20 end end LoopA7 B7 C7 D7 E7 F7 G7 Y coordinate (mm) −265 −226 −149 −72 0 72 149 226265 Arrangement m = 1 ◯ ◯ ◯ ◯ ◯ ◯ ◯ of slots 6a m = 2 ◯ ◯ ◯ ◯ (◯:slotted) ◯ ◯ ◯ m = 3 ◯ ◯ ◯ ◯ ◯ ◯ ◯

Referring to Table 1, exemplary arrangements for slots 6 a are shown form=1, 2, 3, where the distance d between adjacent slots 6 a is d=m·λp/2.For example, for m=1, a slot 6 a can be provided at any of the points onslot antenna 6 onto which the positions of loops A7 to G7 in thestanding wave in interior space 20 are orthogonally projected.

Referring to FIG. 3, for the presence simulation, two plates ofdielectric 5 p and 5 q were disposed symmetrically relative to Ycoordinate zero, because greater surface area of dielectric 5 impairsthe strength of dielectric 5. Dielectrics 5 p and Sq were formed ofalumina (Al₂O₃) with a relative dielectric constant of about 9. Further,the distance d between slots 6 a was d=λp/2, and each of the loops inthe standing wave except D7, i.e. A7, B7, C7, E7, F7 and G7 had a slot 6a on slot antenna 6 directly below.

No slot 6 a was provided at the position on slot antenna 6 that isdirectly below loop D7 in the standing wave partly because a waveguide 3was provided above loop D7 in the standing wave for introducing amicrowave into interior space 20. A slot 6 a provided at such a positionmay significantly affect propagation properties of a microwavepropagated with a 90° change in its direction of advance in interiorspace 20. Another reason is that the portion of slot antenna 6 directlybelow loop D7 in the standing wave was advantageously utilized as asupport for separated dielectrics 5 p and 5 q.

The plasma processing apparatus for the present simulation has asymmetry relative to Y coordinate zero. Accordingly, the descriptionbelow refers primarily to the region of Y coordinates zero and greater.

Interior space 20 filled with air has a relative dielectric constant ofabout one. Consequently, wavelength λq of a microwave formed withindielectric 5 p is shorter than wavelength λp of a microwave formed ininterior space 20. Since wavelength λp of the microwave in interiorspace 20 is already decided, the positions of loops in the standingwaves can easily be matched by multiplying λp by an integer/integer toprovide a wavelength λq of a microwave in dielectric 5 p. In thisexample, arrangements were considered for which wavelength λq of amicrowave in dielectric 5 p was equal to λq multiplied by ½, i.e. 77 mm.

Table 2 shows exemplary trial positions for loops in a standing wave indielectric 5 p with respect to loops D7 to G7 in a standing wave ininterior space 20. TABLE 2 Standing wave in Loop D7 E7 F7 G7 interiorspace 20 With (◯) or without (X) slot 6a X ◯ ◯ ◯ Y coordinate (mm) 0 . .. 72 . . . 149 . . . 226 . . . Trial loop Trial 1 TE(5, X) a5 b5 c5 d5e5 positions in Trial 2-1 TE(6, X) a6 b6 c6 d6 e6 f6 standing wave inTrial 2-2 a6′ b6′ c6′ d6′ e6′ f6′ dielectric 5p Trial 3 TE(7, X) a7 b7c7 d7 e7 f7 g7

Table 2 shows the Y coordinates for loops D7 to G7 in the standing wavein interior space 20, whether these positions have a slot 6 a or not,and exemplary trial positions for loops in the standing wave indielectric 5 p.

Trial 1 represents a microwave of the TE (5, t) (t is an integer) modein dielectric 5 p, Trials 2-1 and 2-2 each represent a microwave of theTE (6, t) (t is an integer) mode in dielectric 5 p, and Trial 3represents a microwave of the TE (7, t) (t is an integer) mode indielectric 5 p. For example, in Trial 3, loops a7 to g7 are formed inthe standing wave in dielectric 5 p.

To consistently process substrate 9 placed in processing chamber 13,greater surface area of dielectric 5 p is preferable. Consequently, asimulation was conducted for Trial 3 to decide the configuration andrelative dielectric constant of dielectric 5 p.

Specifically, referring to FIGS. 2 and 3, a beam 1 b was provided at Ycoordinate zero for supporting dielectrics 5 p and 5 q separated fromeach other. The required width C of the side of beam 1 b that faces slotantenna 6 was determined to be 10 mm or above to provide sufficientstrength. Suppose that loop b7 in the standing wave in dielectric 5 isformed at Y coordinate 72 mm, at which loop E7 is formed in the standingwave in interior space 20, and slot 6 a is provided there, i.e. at Ycoordinate 72 mm. Then, the distance from that slot 6 a to that end ofdielectric 5 p which faces dielectric 5 q is required to be 67 mm orbelow. The distance between loops b7 to d7 in the standing wave is 77mm, and thus the maximum size of dielectric 5 p in the Y direction is288 mm.

Further, larger width of dielectric 5 p (in the X direction) is desiredin order to provide larger surface area of dielectric 5 p, althoughrestrictions such as the distance between adjacent dielectrics in the Xdirection need to be taken into account. Moreover, since processingchamber 13 is at high temperatures under vacuum or at low pressure,dielectric 5 p is required to have a certain thickness to preventdielectric 5 p from breaking. In addition, to allow dielectric 5 p to besupported at an aperture 1 a formed in chamber lid 1, the bottom ofdielectric 5 p is partially cut. Thus, local wavelength changes of themicrowave caused by that configuration also need to be taken intoconsideration.

In view of the above, an electromagnetic field simulation was conductedwith regard to the geometry of dielectric 5 p where the standing waveformed in dielectric 5 p had modes such as TE (7, 0), TE (7, 1) and TE(7, 2). Here, the configurations of inlet waveguide 4, slot antenna 6,slot 6 a and dielectric 5 p, as well as the relative dielectric constantof dielectric 5 p were input to the computer to provide distributions ofthe intensity and direction of an electric field of a microwave.

Several electromagnetic field simulations were reviewed and one suitableconfiguration of dielectric 5 p was extracted with dimensions of 283 mmin the Y direction, 80 mm in the X direction, and 15 mm in the Zdirection.

Further, another electromagnetic field simulation was conducted withonly a change in the position of slots 6 a. The results indicated thatthe mode of the standing wave formed in dielectric 5 p was almostindependent from the position of slots 6 a, and generally remained theTE (7, 1) mode. Moreover, the microwave formed in dielectric 5 p had awavelength of about 77 mm, which indicates that loops in the standingwave formed in interior space 20 appeared at a distance of about 77 mmand loops in the standing wave formed in dielectric 5 p appeared at adistance of about 39 mm.

Consequently, the number of slots 6 a each provided at a positioncorresponding to loops in both standing waves in interior space 20 anddielectric 5 p can be maximized by providing slots 6 a at Y coordinates72 mm, 149 mm and 226 mm. Accordingly, for the entire slot antenna 6,slots 6 a were provided at Y coordinates −226 mm, −149 mm, −72 mm, 72mm, 149 mm, and 226 mm.

The size of slot 6 a in the Y direction affects the amount of radiationof a microwave toward processing chamber 13. Accordingly, a simulationwas conducted to decide the size of slot 6 a in the Y direction thatwould result in a substantially uniform amount of radiation of amicrowave directed to processing chamber 13 from each of slots 6 a.

Electric fields were measured in a plasma processing apparatus having aconfiguration as provided from the above simulation. The resultsconfirmed the ability to efficiently introduce microwave energy intoprocessing chamber 13.

The wavelength of the microwave in dielectric 5 was about 78 mm andslightly different from the wavelength of a microwave in a dielectricfrom the simulation. However, when the position of loop F7, for example,in the standing wave in interior space 20 is matched with the positionof loop d7 in the standing wave in dielectric 5 p, the differencebetween the positions of the loops in both standing waves is about 1 mm.This value can be considered sufficiently small compared with thewavelength of the microwave. In addition, considering the fact thatslots 6 a were constructed with a certain dimension (in the Ydirection), such a difference can be regarded as not significantlyaffecting the propagation efficiency of a microwave.

Slots 6 a of a predetermined dimension each provided at a position asdetermined according to the above design guideline enabled microwaveenergy to be efficiently introduced into processing chamber 13, whichhelped increase the range of conditions (pressure range, for example)for generating a plasma, thereby enabling the construction of a plasmaprocessing apparatus using still less power for generating a plasma.

It should be noted that the size of inlet waveguide 4 and dielectric 5,as well as the number of slots 6 a, for example, are a design choicebased on the size of the plasma processing apparatus and are not limitedto the values mentioned above. Further, the slots were provided on the Eplane (the plane parallel to the electric field in a square waveguide)of inlet waveguide 4, although similar advantages can be achieved byproviding slots on the H plane (the plane parallel to the magnetic fieldin a square waveguide), since there is no change in the wavelength ofthe microwave in interior space 20.

Further, dielectric 5 may also be formed by other dielectrics such asAlN or SiO₂. By selecting the material of dielectric 5, the relativedielectric constant of dielectric 5 can be changed. Moreover, whendielectric 5 is predominantly composed of alumina as above, the relativedielectric constant of dielectric 5 can be regulated by changing theproportion of alumina therein or the composition of other components. Inthis way, with the configuration and dimension of dielectric 5 being thesame, a dielectric having a specified relative dielectric constant canbe selected as the material of dielectric 5 so as to provide a microwavein dielectric 5 at a desired wavelength. Thus, the flexibility indesigning a plasma processing apparatus can be improved. Further, bymounting a dielectric at interior space 20, the relative dielectricconstant of interior space 20 can be regulated as appropriate, whichwill further improve the flexibility in designing a plasma processingapparatus.

Although two dielectrics 5 for one interior space 20 were described, anynumber of dielectrics 5 will allow a plasma processing apparatus to beconstructed with improved propagation efficiency of a microwave as faras slots 6 a are provided according to the above design guideline.

Further, although in the present embodiment a plasma processingapparatus used as dry etching equipment was described, the presentinvention, which provides a technique to efficiently direct a microwaveinto a processing chamber using a slot antenna, can be applied to anyequipment that performs plasma processing, such as deposition equipmentand ashing systems.

Next, the advantages of the plasma processing apparatus according to thepresent embodiment were confirmed by other simulations for comparison.The simulations for comparison used different positional relationshipsbetween slots 6 a and the standing waves formed in interior space 20 anddielectric 5 for comparison of the propagation efficiencies of amicrowave for the respective positional relationships.

Referring to FIG. 4, each slot 6 a was provided at a position wherenodes in the standing waves in interior space 20 and dielectric 5matched up. Here, the microwave had a very low propagation efficiency,presumably because greater part of the energy of the microwave wasreflected by slot antenna 6 when coming into slot 6 a.

Referring to FIG. 5, each slot 6 a was provided at a position for a loopin the standing wave in interior space 20. However, each slot 6 a wasprovided at a position for a node in the standing wave in dielectric 5.In this case, the microwave had a propagation efficiency much lower thanthat for the simulation according to the present embodiment, but higherthan that for the simulation shown in FIG. 4, presumably becausemicrowave energy was efficiently propagated from interior space 20 toslot 6 a but major part of the energy of the microwave was reflectedwhen coming into dielectric 5 from slot 6 a.

Referring to FIG. 6, each slot 6 a was provided at a position for a loopin the standing wave in interior space 20. However, each slot 6 a wasdisplaced from positions for loops and nodes in the standing wave indielectric 5. Here, the microwave had a propagation efficiency muchlower than that for the simulation according to the present embodiment,but higher than that for the simulations shown in FIGS. 4 and 5,presumably because microwave energy was reflected when coming intodielectric 5 from slot 6 a similar to the case shown in FIG. 5 but in asmaller amount.

Second Embodiment

A plasma processing apparatus according to a second embodiment isconstructed similarly to the plasma processing apparatus in the firstembodiment except that the plasma processing apparatus of the secondembodiment provides a slot 6 a that will result in electric fields inone and the same direction for those loops in standing waves which areformed within interior space 20 and dielectric 5 and are opposite eachother with respect to the same slot 6 a.

In the plasma processing apparatus according to the second embodiment ofthe present invention, the electric fields of first and second standingwaves have almost the same direction at positions each corresponding tothose loops in the first and second standing waves which are projectedto the same slot 6 a.

A plasma processing apparatus constructed as above can minimize thechange in the direction of an electric field for any of the apertures,thereby minimizing reflected wave. Thus, microwave energy can beintroduced into processing chamber 13 still more efficiently.

A computer simulation was conducted as below to enable the designing ofan actual plasma processing apparatus in the present embodiment. FIG. 7is a cross sectional view corresponding to FIG. 3 of the firstembodiment. It should be noted that the near-circles and the symbols inthe middle of the near-circles in FIG. 7 should be interpreted in asimilar way to the illustration of FIG. 3 of the first embodiment.

Referring to FIG. 7, an interior space 20 defined by inlet waveguide 4had dimensions of 16 mm in the X direction, 530 mm in the Y directionand 71.5 mm in the Z direction. Here, the microwave in interior space 20had a wavelength λp of about 234 mm, and loops A5 to E5 in the standingwave in interior space 20 were formed at a distance of about 117 mm. Themajor component of the electric fields for loops A5 to E5 in thestanding wave had a direction consistent with the X direction and theelectric fields for the adjacent loops in the standing wave had oppositedirections.

Dielectric 5 was composed of dielectrics 5 p and 5 q having aconfiguration as derived from the simulation of the first embodiment.The microwave in dielectric 5 p had a wavelength λq of about 77 mm, andloops a7 to g7 in the standing wave in dielectric 5 p were formed at adistance of about 39 mm. The positions of loops D5 and E5 in thestanding wave in interior space 20 coincided with the positions of loopsb7 and e7 in the standing wave in dielectric 5 p. The major component ofthe electric field for loops a7 to g7 for the standing wave indielectric 5 p also had a direction consistent with the X direction, andthe electric fields for the adjacent loops in the standing wave hadopposite directions.

Consequently, slots 6 a were formed directly below loops A5, B5, D5 andE5 in the standing wave in interior space 20 such that the electricfields for opposite loops in the standing waves with respect to one andthe same slot 6 a had the same direction.

An electric field was measured in a plasma processing apparatus having aconfiguration as derived from the above simulation. The resultsconfirmed the ability of introducing microwave energy into processingchamber 13 still more efficiently.

It should be noted that the embodiments disclosed herein are by way ofexample and not limitative in any way. The scope of the presentinvention is set forth by the claims and not by the above description,and is intended to cover all the modifications within a spirit and scopeequivalent to those of the claims.

As described above, the present invention provides a plasma processingapparatus that improves the propagation efficiency of a microwave passedthrough an aperture of a slot antenna, thereby allowing microwave energyto be efficiently introduced into a processing chamber.

INDUSTRIAL APPLICABILITY

The present invention is applicable to dry etching equipment, depositionequipment and ashing systems used in manufacturing processes of a liquidcrystal display device, solar cell or the like.

1. A plasma processing apparatus comprising: a processing chamber forperforming plasma-assisted processing; microwave introducing meanshaving an interior space in which a first standing wave of a microwaveis formed by means of resonance, the microwave introducing meansdirecting the microwave to said processing chamber; a dielectricprovided between said processing chamber and said microwave introducingmeans and adjacent said interior space for directing the microwave intosaid processing chamber, a second standing wave of the microwave beingformed within the dielectric by means of resonance; and a slot antennahaving an aperture through which the microwave is passed from saidinterior space to said dielectric, the slot antenna covering a side ofsaid dielectric that faces said interior space, wherein said aperture isgenerally located at a point where the position of a loop in the firststanding wave orthogonally projected to said slot antenna coincides withthe position of a loop in the second standing wave orthogonallyprojected to said slot antenna.
 2. The plasma processing apparatusaccording to claim 1, wherein a plurality of apertures are provided at adistance d, the distance d satisfying d=m·λp/2 (m is a natural number)and d=n·λq/2 (n is a natural number), where λp is the wavelength of themicrowave in said interior space in which the first standing wave isformed, and λq is the wavelength of the microwave within said dielectricin which the second standing wave is formed.
 3. The plasma processingapparatus according to claim 1, wherein the first and second standingwaves have electric fields substantially in one and the same directionat those loops in the first and second standing waves which areprojected to one and the same aperture.